Enhanced detection of paramagnetic fluorine-19 magnetic resonance imaging agents using zero echo time sequence and compressed sensing

Journal Article · Tue Mar 29 00:00:00 EDT 2022 · NMR in Biomedicine

DOI:https://doi.org/10.1002/nbm.4725· OSTI ID:1976364

Chen, Jiawen ^[1]; Pal, Piya ^[1]; Ahrens, Eric T. ^[1]

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1. Univ. of California, San Diego, CA (United States)

Fluorine-19 (¹⁹F) magnetic resonance imaging (MRI) is an emerging technique offering specific detection of labeled cells in vivo. Lengthy acquisition times and modest signal-to-noise ratio (SNR) makes three-dimensional spin-density–weighted ¹⁹F imaging challenging. Recent advances in tracer paramagnetic metallo-perfluorocarbon (MPFC) nanoemulsion probes have shown multifold SNR improvements due to an accelerated ₁₉F T₁ relaxation rate and a commensurate gain in imaging speed and averages. However, ¹⁹F T₂-reduction and increased linewidth limit the amount of metal additive in MPFC probes, thus constraining the ultimate SNR. To overcome these barriers, we describe a compressed sampling (CS) scheme, implemented using a “zero” echo time (ZTE) sequence, with data reconstructed via a sparsity-promoting algorithm. Our CS-ZTE scheme acquires k-space data using an undersampled spherical radial pattern and signal averaging. Image reconstruction employs off-the-shelf sparse solvers to solve a joint total variation and -norm regularized least square problem. To evaluate CS-ZTE, we performed simulations and acquired ¹⁹F MRI data at 11.7 T in phantoms and mice receiving MPFC-labeled dendritic cells. For MPFC-labeled cells in vivo, we show SNR gains of ~6.3 × with 8-fold undersampling. We show that this enhancement is due to three mechanisms including undersampling and commensurate increase in signal averaging in a fixed scan time, denoising attributes from the CS algorithm, and paramagnetic reduction of T₁. Importantly, ¹⁹F image intensity analyses yield accurate estimates of absolute quantification of ¹⁹F spins. Overall, the CS-ZTE method using MPFC probes achieves ultrafast imaging, a substantial boost in detection sensitivity, accurate ¹⁹F spin quantification, and minimal image artifacts.

• Research Organization: Univ. of California, San Diego, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC); National Institutes of Health (NIH)
• Grant/Contract Number: SC0022165; R01-EB024015; R01-CA139579
• OSTI ID: 1976364
• Journal Information: NMR in Biomedicine, Vol. 35, Issue 8; ISSN 0952-3480
• Publisher: Wiley
• Country of Publication: United States
• Language: English

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